Rolling of thin gauged material



Jan. 13, 1948. s. GAGE EI'AL 2,434,553,

ROLLING OF THIN GAUGED MATERIAL 0 Filed llay 20, 1943 gwudmlqu GORDONGAGE DAvw HuaHs Patented Jan. 1a, 1948 ROLLING F THIN GAUGE!) MATERIALGordon Gage and David Hughes, Butler, Pa... as-

signors to The American Rolling Mill Company, Middletown, Ohio, acorporation of Ohio Application May 20, 1943, Serial No. 487,768

2 Claims.

. the working rolls is transmitted by rotating elements to rigid beamsextending in the direction of the axis of the rolls. For many uses it isundesirable or uneconomical to produce the material in narrow widths,and as to the special beam backed mills they are not generally availableas yet.

While our invention is not confined to this field of utility, we maymention that it is being presently used for the formation of wide butvery thin silicon steel strip .003 inch or less in thickness. Suchexceedingly thin silicon steel strip has come to be of commercialimportance for the manufacture of certain types of high frequency,

transformer cores and for other special uses. It may be noted also thatsilicon steel by reason of its tendency to hardness and brittleness is adiflicult material to cold roll. We shall describe our invention in anexemplary embodiment having to do with the manufacture of thin siliconsteel strip of the character to which reference has just been made, butit will be understood that it may be used in other fields of utility.

As is well known, in the cold rolling of wide strip there is, asrespects any given metal of any given metallurgical characteristics inany given mill, 2. gauge limit below which cold rolling will not beeffective, due largely to the spring of the rolls. This phenomenon isnot entirely confined to cold rolling mills of course, and Just as packrolling is practiced in hot mills, attempts have not resulted in theprovision of a mode of operation or mechanism whereby thin, wide, hardmetal strips could be produced with great accuracy on standard rollingequipment, even with the addition of extra reels and the like; but it isa fundasingle pass to gauges in the neighborhood of .003'

2 mental object of our invention to provide such a mode of operation.

It is an object of our invention to provide means and a method wherebyahard metal strip of a. gauge conveniently produced by conventional coldrolling operations can be carried down in a inch or less with greataccuracy.

It is an object of our invention to provide a means and method for doingthis wherein the additional materials employed, themselves become usefulfor reduction in a similar manner to the same or similar light gauges insubsequent operations.

It is an object of our invention to provide a mode of proportionallyrolling a combined work'- piece through the use of tension whereintension is correlated not only to the strengths of the workpieceportionsbut also to the proportional reductions accomplished.

-It is an object of our invention to provide a mode of treatment,preparation, combination and rolling for a composite workpiece withequipment which may not be characterized by a plurality of reels orcoilers on both sides of the mill and wherein discrepancies in theinitial length of concurrently coiled workpieces may be compensated inways hereinafter set forth. These and other objects of our inventionwhich will be set forth hereinafter or will be apparent to one skilledin the art upon reading these specifications, we accomplish by thatcertain mode of operation and with those apparatus modifications ofwhich we shall now describe certain exemplary embodiments. Reference ismade to the drawings which form a part hereof in which:

Figure 1 is a diagrammatic representation of a step of preparing a stripsurface for combination with another strip.

Figure 2 is a diagrammatic showing, serving to. illustrate the .step ofproducing a matched or composite coil and the step of rolling that coilwhen the mill is reversed.

Figure 3 is a diagrammatic representation'of the passage of a pluralityof strips simultaneously through a rolling mill wherein the entering andleaving tension on each strip can be separately controlled.

In an exemplary procedure under our invention, and using the exemplaryequipment hereinafter set forth, we first prepare two strips of sili-.con steel of different gauges, one oi the strips being .019 inch inthickness and the other being .005 inch in thickness. These strips willbe -of sheet width, say 2 4 inches or more depending, of course. on theavailable equipment for producing them and the width of the mill to beused for affecting reduction to very thin gauges in accordance with theteachings of our process. The strips will be long enough to give themill a good productive capacity-a coil of the heavier material may weigh6000 lbs. or more.

The strips themselves may be made by any of the current strip processes.Ordinarily these will comprise the forming of slabs from ingots, the hotrolling of the slabs to intermediate gauge strips and the cold rollingof the-strips singly to the gauges desired, with such annealings andpickling between the other steps as may be a part of good IOllll'ie;procedure. or as may be dictated by some special initial or ultimatequalities of the material. For example,there are a number of recognizedprocesses for the production of silicon steel which (usually inconnection with a final heat treatment) are relied upon to impartparticular magnetic or other qualities to the material. These will notbe herein discussed. They are applicable to and may be practiced inconnection with the novel steps of our invention which will be setforth; but they form no limitation thereon.

The thinner of the two strips, especially if its thickness is such ascannot conveniently be made by ordinary cold rolling processes, may beformed as an incident to ourprocess as will be explained. I

The two strips--in the exemplary embodiment having respectively gaugesof .019 and .005 inch-have surfaces which are clean, 1. e., free fromscale, though not necessarily free from a thin uniform oxide film, andare preferably, though not necessarily, in annealed condition. Thesofter the material, the easier it is to work; but the nature andcharacter of the annealing operation. if any, does not form a limitationupon Our procedure and may be such as is essentially dictated by otherdesired characteristics, e. g., the magnetic properties where siliconsteel is the' material worked upon. Bright annealing of cold rolledstock will in the preparation of our starting pieces usually render apickling unnecessary; It is not necessary that out starting materialshave what is known as a cold-rolled surface, but in manv instances thisis helpful.

As shown in Fi ure 1, we may take a coil of open'annealed s licon steelstock of .019 gauge, say 25 inches slit width, as at I, and pass itthrough a mill 2, having an emery cloth wiper dia rammatically indicatedat 3. The emery cloth is located on the top side only with a felt dragon the bottom. The emerv cloth flattens small projections and cleans thetop surface which is later to come in contact with the li hter gau estrip, and in instances is hel ful. It is not necessarv. But precautionsshou d be taken that at least the contacting surfa e of the strip i sutably clean. and the procedure just described is one way of doing this.Any projections on the surface of heavy strip that is to be in contactwith li ht gauge strip will punch holes. in thin strip when the twostrips are given the reducing pass. Also it is advisable that the coilbe carefully rewound as at 4 with even tension.

While we have spoken of passing the strip through the mill 2, this isessentially a matter of convenience, ,for no pressureis applied to the 4to the surface of the strip before recoiling as diagrammaticallyindicated at I.

The coil 4 is now brought around to the entering side of the mill(Figure 2). A coil of open annealed .005 inch silicon steel, preferablyslit to 24 inches in width, is placed on another reel as at B, and thetwo strips are run through 9, double felt wiper as at 1. A double wiperis important, for we have found thatv if two different gauges arematched, using one wiper only through which they concurrently pass,there will be variable friction between the two contacting surfacescaused by non-uniformity of tensions between the pay-off reels and thewiper, mill or recoiler. This not only produces a tendency for thelighter gauge material to run off to the side but also gives a combinedcoil in which the tensions are not uniform.

The two strips from coils 4 and 6, passing through the mill 2, are woundtogether to form a matched coil 8. In this operation constant tension ismaintained between the .005 coil and the wiper and between the .019 coiland the wiper. Once again no pressure is applied to the mill. and it isdoing no work. A small stream of palm oil is preferably played on thetwo strips as they are wound together. This operation also could beperformed on apparatus that did not include a rolling mill.

It will have been noted that the thinner strip is preferably somewhatnarrower than the thicker strip. This is not absolutely essential but ishelp- 1.11 in matching the strips and in producing a combined rollingpiece.

Further, in our exemplary procedure the mill 2 is now reversed anddriven under screw pressure, the matched strips being withdrawn from thecombined roll 8 and separately recoiled as at 4 and 6. Power isseparately applied to the tension mill, fand the mill at this time isdoing no work.

A light stream of palm oil is prefera ly app ied coilers on which coils4 and 6 are positioned, and to the mill and to the reel or coiler whichis paying off the combined strip from the coil 8. During the rollingoperation the double drag I will, of course, be removed. An enteringdrag may be employed if desired but is not necessary, because backtension can be exercised by the coiler holding coil 8. In an exemplaryoperation, with 1200 amperes pull on the mill, at a speed of 150 feetper minute, with a back tension produced by applying 350 amperes to thecoiler holding the combined coil 8 and with forward tension produced byapplying 150 amperes to the coiler holding coil 4, we have concurrentlyreduced the .005 inch strip to a gauge of .003 inch and the .019 inchstrip to .010 inch. During this rolling operation, power will be appliedto the coiler holding coil 8, but the power so applied need be onlysufficient to assure tight and even coiling. The two strips are rewoundseparately as indicated, the movement of material being to the right inFigure 2 and opposite to its direction of motion during the precedingstep of forming the combined coil-8. In the particular operation, on theparticular mill and with the workpieces which we have described. it isnecessary that the tension on the coiler 6 be very light during rolling,that is to say, just enough to keep the strip between the mill 2 and thecoiler 6 from becoming slack and to permit tight and even coiling asaforesaid. The power figures which we have given are thus exemplary forthe particular illustrative procedure which we have outlined.

In our operation the thinner strip is being passed through the millunder tension riding on The particular procedure which we have outlinedis exemplary only and is not limiting. It

is important that the wall thickness of the heavier .strip be initiallyat least three times as thick as that of the thinner strip where twostrips only are being concurrently rolled from a matched coil as at 8containing both strips. In the particular exemplary illustration, thetwo strips were in a similar annealed condition and therefore of asimilar softness. But, it will be obvious that where two strips areconcurrently wound upon a single coil, that strip whichis radially theoutermost in each convolution will be the longer. matched coil toencounter a progressive slackness of the outermost strip when theinnermost is maintained under tension. In'our rolling process this doesnot occur however; and the compensation appears to take place in thebight of the rolls. We have indicated that we apply power to the coilercontaining coil 8, and while we have not separately measured the tensionin the thinner and thicker strips, the fact is that the combined stripsdecoil as though they were one, and without either separation orslackness.

It may be noted from the example given above that the percentagereduction made in each strip is not the same. The .005 strip has beenreduced to .003, while the .019 strip has been reduced to .010. Thetensional conditions were not in this instance the same on the twostrips, either in the absolute sense 01' in proportion to their finishedgauges.

The peculiar behavior of the matched strips is not readily explainableunder ordinary rolling concepts, for as will be evident from thespecific example shown, it seems to involve certain obviousinconsistencies. We do not attempt to explain them. We do know, however,that it is possible to carry a heavier strip through the mill undercontrolled tension and at the same time to cause a lighter strip to ridethrough the mill and be concurrently reduced under the same or differenttensional conditions; that aside from such variables as may beintroduced by composition of the two strips or divergent degrees ofhardness, it is possible to control within limits wide enough foroperability the relative percentages of reduction by controlling thetensional conditions on each strip, and further that where two stripshave been wound upon the same reel or coiler and are concurrently paidtherefrom undertension, that by controlling the tension on the thickerof the strips, the two strips may be caused to pay off and roll as one,where the materials are the .same and of similar hardness, and where thegauges are roughly in the proportions of those set forth and thetensions are roughly in the proportions of those set forth. With otherratios of starting gauges it may be found necessary to control thetension of both pieces on the outgoing side of the mill at suchsubstantial values as will have a definite effect upon the reduction ofeach strip. All other conditions being equal, a substantial variation ofthe tensional conditions on either or both strips will vary the relativepercentage of reduction of the strips during their passage through themill. As might be expected, variations in total tensions will likewiseproduce variations in total or combined reduction.

An advantage of the process set forth in the exemplary embodiment isthat it may be practiced with cold rolling mills which have a pay-oflreel and a tension reel on one side of the mill and one tension reel onthe other side. Mills so equipped One would expect in the decoiling ofa.

exist, and in any event the addition of one tension reel to one side ofthe mill is not a matter of exorbitant capital outlay. But where, to amill having but one tension reel on each side it is possible to add oneor more additional tension reels on each side, the step of producing amatched coil can be eliminated. We have found it possible, as shown inFigure 3, to roll through the mill 2 separately strips from coils 9 andi0, rewinding them separately as at I I and I2. While we have shown therolling of two separate strips in Figure 3, three or more strips may beconcurrently rolled; where the strips are decoiled from and recoiiedupon separate coiling devices to which controlling power may beseparately applied, it then becomes possible in the light of ourteachings to control the relative percentages of reduction'attained inseparate strips of the same or different starting gauges to produce thesame or diflerent finished gauges within a, fairly wide range. It willbe understood, of course, that the thinner the finished gauge of thematerial, the less absolute tension it can stand in proportion to itswidth. When working with exceedingly thin materials or materials whichare brittle in their nature or for any other reason cannot support aheavy tension when they have attained finished gauge, the indicatedprocedure is that of rolling a light strip with a heavy one under suchconditions that the heavy tension may be applied to the heavy strip,while the light strip on the exit side of the mill need not be tensionedbeyond that value which it can support or which is necessary for theproduction of a suitable coil. For reasons which are not clearlyunderstood, the tension on one of the strips being concurrently rolledaffects the rolling of the other strip. When speaking of tensiongenerally, we include back tension as well as forward tension where bothare not employed. Operations under our invention, however, may includethe elimination of forward or back tension on one or more of the strips.

Where two strips are matchedand coiled on a single coiler as describedin the exemplary embodiment, the factor of the different effectivelengths of the two strips as they approach the mill introduces arestrictive factor. Slackness is ordinarily not desired in one of thestrips as it enters the mill. The compensation which has been describedthus dictates either a considerable disparity in the initial gauges ofthe strip or a considerable disparity in forward tension on the twostrips, or both.

The character of the metal being rolled is also a factor in determiningwhat can'be done, as to procedure, and what need be used. as toequipment. We have applied the principles of this invention to therolling of very thin stainless steel strip, the strip being of thefamiliar 18-8 variety, as well as in the rolling of other chromium orstainless steels. Stainless steel is again a hard material which isdlfflcult to reduce to thin gauges; but unlike silicon steel it is notbrittle ducing them to final gauge.

During the rolling operation the strips are decoiled together from thecoil 8 and passed through the mill 2; but instead of being separatelycoiled as at l and 6 (which also of course may be done), we have foundthat the combined strips may be wound together on a single tensioncoiler. During the mill pass the strips are each reduced from .007 inchto .005 inch in thickness. The two strips are not only concurrentlydecoiled from coil 8 and passed through the mill as a unit, but areconcurrently recoiled onto the same coiler,,'as for example at 4. Thisis of advantage where equipment is available consisting of a suitablemill with one tension coiler on each side. The stainless steel has veryhigh tensile strength so that even at the light gauges it will withstandcomparatively high tensions developed in the coilers supporting coils 8and 4. In fact. the tensile strength of the stainless steel is usuallyas much as two or three times the tensile strength of silicon steelstrip, gauge for gauge.

The strips decoil and recoil as a unit and without separation providingthe forward and back tensions are properly correlated to the totalreduction and the strength of the strips, the compensation againappearing to occur in the bight of the rolls. The back tension on theouter strip is presumably less on the entering side of the mill while onthe exit side of the mill the outer strip presumably sustains thegreater part of the forward tension. Yet in the particular exemplaryprocedure the percentage reduction in each strip is the same.

After the concurrent recoiling during rolling, the two strips ofstainless steel rray be separated from each other on a difierent unit,and each strip maybe given a light, single skin pass to obtain a highsurface finish as discussed hereinafter.

There are certain advantages derivable from concurrently rolling twostrips of different starting gauge. In the exemplary embodiment the .019material is accurately reduced to .010 inch. This is a convenientintermediate gauge for further single strand cold rolling operationssuch, for example, as may result in the provision of .005 strip. Also,our invention is not confined to the rolling of two strips concurrentlyor to the rolling of gauges such as those set forth in the exemplaryembodiment. The operation may be so carried on that while a coil offinished light gauged material is made in each mill operation under ourinvention, one at least of the heavier strips is reduced to such a gaugethat it can be employed as the lightest strip in a subsequent repetitionof our process. Thus it will be seen that the cold rolling accomplishedduring our process on the heavier strip or strips is not lost asmechanical work but simply forms one of the stages of reduction of suchstrips incident to re- Needless to say, the thicker strip or stripsemployed in our process may be re-annealed before further processing andwill usually be re-annealed.

The skilled roller familiar with his equipment will be able to determinea range of initial thicknesses for composite workpieces to be rolled inan eflicient manner on his mill. From this he will be able todevise-suitable composite workpieces apportioning to each part itspercentage of the total or combined gauge so that within the limits ofthe tensional variations which he can produce with his equipment, he.can control the relative percentages of reduction to give him hisdesired finished gauges. It will, of course, be understood that ourprocess is applicable to 8 the simultaneous production of finishedProducts of different gauges. Thus, if finished silicon steel is desiredin gauges of .010 and .003 inch, the specific example which we havegiven is effective in the simultaneous production of finished siliconsteel in two different but equally accurate gauges.

Our invention is not limited to the concurrent rolling of strips of thesame composition, but within reasonably wide limits may be applied tothe concurrent rolling of dissimilar metals, due allowance being madefor such differences as may exist in their softness and reliability.

Where two strips are employed, one surface of each at the conclusion ofour process will have an "open" surface rather than a cold rolledsurface. Where more than'two strips are employed, an intermediate stripor strips will have no cold rolled surface at all. For many uses theabsence of a cold rolled surface is not objectionable; but it can in anyevent be remedied by giving to the finished strips separately a "skin orsurfacing pass in a cold mill, which is one producing no elongation butmerely compressing and smoothing the surface of the stock.

Modifications may be made in our invention without departing from thespirit of it.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent is:

1. A process of producing thin wide strip material which comprisescleaning the surface of a plurality of strips, one at least being ofheavier gauge than another, winding said strips into a composite coilunder equal tension, withdrawing said strips together from saidcomposite coil, passing said strips through a rolling mill andconcurrently reducing them, separately coiling said strips on the exitside of said mill and applying forward tension at least to said heavierstrip.

2. A process of producing thin wide strip material which comprisescleaning the surface of a plurality of strips, one at least being ofheavier gauge than another, winding said strips into a composite coilunder equal tension, withdrawing said strips together from saidcomposite coil. passing said strips through a rolling mill andconcurrently reducing them, separately coiling said strips on the exitside of said mill and applying forward tension to both strips, theforward tension applied to said heavier strip being greater in amountthan the tension applied to a lighter strip, and controlling thetensional relationship in such manner as to avoid slackness in any ofthe strips as they enter the mill and in such manner as to maintain afixed relationship of proportional reductions in the strips.

. GORDON GAGE. DAVID HUGHES.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

